This invention relates to lubricating oil compositions. More particularly, this invention relates to lubricating oil compositions containing relatively low levels of sulfur.
In the ever-increasing effort to reduce exhaust gas emissions from internal combustion engines, manufacturers of gasoline powered engines and diesel engines are turning more and more to using exhaust gas after treatment devices (e.g., catalytic converters, particulate traps, etc.) to reduce emissions. A problem with using such devices, however, is that lubricating oil compositions containing relatively high levels of sulfur eventually decompose and the decomposition products of these lubricants, including the sulfur, eventually enter the after treatment device and often contribute to damaging the device. Additionally, the allowable level of sulfur in diesel and gasoline fuels is expected to drop to 15 parts per million (ppm) with zero-sulfur fuel already being required in select locations. Therefore, a substantial portion of the sulfur in the emissions of these engines can be expected to be attributed to sulfur in the lubricant. This has resulted in pressure to reduce sulfur levels in the lubricating oil compositions used in these engines.
The present invention provides a solution to this problem by providing lubricating oil compositions containing relatively low levels of sulfur.
This invention relates to a lubricating oil composition, comprising: (A) a base oil; and (B) a phosphorus-containing compound represented by the formulae 
wherein in Formulae (B-I) and (B-II), R1, R2 and R3 are independently hydrogen or hydrocarbyl groups, and a, b and c are independently zero or 1; the lubricating oil composition being characterized by a sulfur content of about 0.01 to about 0.25% by weight. In one embodiment, the lubricating oil composition further comprises (C) an acylated nitrogen-containing compound having a substituent of at least about 10 aliphatic carbon atoms. In one embodiment, the composition further comprises (D) an alkali or alkaline earth metal salt of an organic sulfur acid, a carboxylic acid or a phenol. In one embodiment, the composition further comprises (E) an alkali or alkaline earth metal salt of a hydrocarbon-substituted saligenin. In one embodiment, the composition further comprises (F) a metal salt of a phosphorus-containing compound. In one embodiment, the composition further comprises (G) a dispersant viscosity index modifier. In one embodiment, the composition further comprises (H) one or more additional optional additives. The inventive composition may be made by blending components (A) and (B), and optionally one or more of components (C) to (H), using known blending techniques and any order of mixing or addition.